Cam operated machine



Feb. 16, 1937. L, E T HA j 2,070,633-

CAM OPERATEP MACHINE 1, Filed March 9. 1934 2 Sheets-Sheet 1 air Witness 2 Vfig gz Feb. 16, 1937. L. E. TOPHAM 2,070,633

I CAM OPERATED MACHINE Filed March 9. 1934 2 Sheets-Sheet 2 lnveniof' Wiiiiess Patented Feb. 16, 1937 UNITED STATES CAM OPERATED MACHINE Laurence .E. Topham, Wenham, Mass, assignor.

to United Shoe MachineryCorporation, Pater- 7 son, N. J a corporation of New Jersey Application March 9, 1934, Serial 'No. 714.782

' 2 Claims. (01. ,74-53)- The present invention relates to machines operated .by slotted or grooved cams and is herein illustrated as applied to a lockstitch outsole shoe sewing machine of the type described in the patent to French and Meyer No. 412,703.

The object of the invention. is to provide new and improved slot-forms'for' actuating cams in a machine of the classreferredto by meansof which the machine will. operate :morequietly; at a higher speed, and more reliably than hereto-'- fore.

In any machine ope'ratedbyan open type of cam having aspring pressed "follower; impact during movement'ofxtheicam may be produced by too sudden a changeiin'thevelocityofimovei ment imparted to the follower by the cam. The impact between the follower and the roam .in-' creases with the square of the change in velocity, sothat difiiculty of this-nature is directly'reduced by lowering the speedzat which the machineis operated. It "is the usual practise, in.order t oi increase the speed of machines operated by such cams, to modify the form of the cam so that the followerwill start and stop. more'gradually, the inertia of the follower being more slowly' over-' come.

In any machine operated by the closed or slotted type of cam, in'which'the follower is guided without being yieldingly forced against either side of the slot, a. certain amount of lost motion between the parts must be provided to prevent excessive friction. Impact of the follower against the slot sides of a closed cam may be producedby a number of causes in addition to'starting or stopping the follower movement too' suddenly. Speed of rotation "of a closed cam'may'not beta directfactor in effecting sudden change in ve-' locity of the operated parts as the follower shifts itspr-essure of engagement from one side of the cam slot to the other, but impact may take place with considerable forceeven below speeds .at which a machine equipped with an open .c-am of the same form may operate'with relatively no noise. The causes of impactin aclosed cam may; also change while the machine. is operating so that even though the'cam slot is of a shape which is advantageous for one set'of operating conditions, it will be ineffective'in preventingun desirable impact undersother normal conditions of machineoperation.

Accordingly,- the present invention contemplates the provision in a sewing or similar type of machine, in which an actuating cam is pro-' vided with a continuous-slot forguiding afollower. each ndividual mc ems i f w h s uch those skilled in the art.

. 22 is oscillated by an arm 24 secured to one end at any-point in the rotation of the cam 10 foria a character that the degree of impact caused as the follower "shifts between engagement of the slot sides will occur with certainty along a predetermined portion ofthe cam where the impact will be maintained below a predetermined minimum limit with changes in speed of operation, friction inthe machine, and amount ofwork performed by the machine.

Other features of the invention'consist of certain novel and improved constructions andar- 10 rangements of parts, hereinafter described and particularly pointed out in the claims, the advantages of which will bereadily understood by In theaccompanyingdrawings, Figure 1 isa 15 view-in side elevation with certain parts broken away and shown in section, of a sewing machine equipped with cams embodying the features of the-present invention, and Figure 21s a diagrammatic illustration of the form of cam slot move- 20 ment employed in the machine shown in Figurel.

The machine illustrated .in Figure 1 of the drawingsis a lockstitch outsole shoe sewing machine ofa-type morefully described in the patent above referred to, and comprises operatedparts 25 and a series of cams, one of which is indicated at I0, keyed to a cam shaft l2 rotatably mounted in the machine. The operated parts include a. curved hook needle M, a curved awl [6, a shuttle l8, a take-up 20 and other stitch forming and work feeding devices. The operated parts are moved through individual cycles of operation in proper timed relation to form a seam in the work, the movement of each part being controlled'by suitable continuous cam slots formed in the cams.

As an example of one set of operated parts, the take-up 2|] is illustrated as being in the form of an arm fixed to a shaft 22 rotatable in a bearing on the frame of the machine. The take-up shaft of the shaft and connected by means of a link 26 to one arm of a cam operated lever 28 journall'ed on a fixed'stud 30. The other arm of the lever 28 carries a short shaft 32 on which is rotatably: mounted a cam follower roll 34 positioned between the sides 36 and 38of a cam-slot formed in the cam Ill. The operated part ZILtheVarm 24, link 26, lever 28 and the cam'follower' roll 34 comprise a moving mechanical systemhaving certain'physical characteristics of mass,- elasticity and friction, the mass being represented by the inertia of the parts according to their. manner of movement. The degree of impact in the moving system, due to change in velocity of the follower given speed of the shaft [2, is proportional to the mass of the moving system, but impact from this cause may be reduced, as previously explained, by simply reducing the acceleration of the folj lower at the beginning and end of its movement.

Another cause of impact in the mechanical system results from clearance between the sides of I the slotand the follower 34, and in the bearings the other, they act as a separatemechanicjal system independently of the cam,'according to their I individual physical characteristi.cs,*-' and in so doing, may set up a series of more or less sharp andconnections of themechanical system; Due to this clearance, a certain amount of lost motion is possible, permitting a momentary departure-- in velocity of the'operated parts'from that velocity pres'cribedby the shape of the ca'm' slot;

During the brief period in'which the operated parts move from one limit of theirllost 'motion to impacts which .may be increased" in intensity along certainparts of the slotjor may cause un desirable oscillations between individual members V of the system at unexpectedtime's; 1

d According tot-he presentinvention it is possible to so formithe cam slot that impact due to the physical characteristics of the mechanical system may be made'to occuralong one portion only of the cam where the, forcecreating the impact is reduced to'a minimum limit. 1

Ina sewing machina'a'ny operated part, such as the take-up '20 and :the connecting links "bea tween the operated part and actuating camfol lower havea certain amount ofmass and elasticity which can be' -measured. The elasticityjto getherwith'thefmass off'the parts, may cause the I mechanicalsystein including the parts-to oscillate at a fixed frequency, *For any elementary uni directional movement ;ofthe cam follower 34 be:

tweenthe cam slot'p ortion 40 and anyother portion 41 asindicated diagrammatically in Figure 2,

'apertainforce' or pressure is imparted to the follower during the first part of the movement by V engagement with one side 36'of' the slotthe're after the ,force is diminished'to' zero and sufiicient forceapplied in the opposite direction by the other side 38 of the slotjto again bring thefollower 34 toj rest. f The ,moving force may be diminished progressively almost to' Zero at a relatively high rate near the time the velocity of the follower in thellineof follower movement reaches its maximum value and becomes uniform, at which time the follower maybe guidedby a portion 44 of the slot somewhere near the middle of its movement.

If the moving force is diminished at too high a rate, the elasticity of the moving system will cause a rebound of the follower, characterized by .a rapid engagement with alternate sides-of the slot.

It is, therefore,essentialin order to preventthis rebound, that v5 the moving force be. diminished only as fast as the massand elasticity of the moving s'ystemwill permit the follower 34 to conform with the motion 7 imparted Joy-the cam. The

' length of time required for diminishing the force along portion 44iis, therefore, chosen to at'least equalfon'e half 'the natural time period of free oscillation=of the mechanical system. To in- "crease thefactor or aret this time period may be Ydotrbledwithout adding greatly to the total.v

time required for the/entire 'movenrent between "and 42.; For all practical purposes, the amount 1 c. of massiand elasticity of the voperatedparts may beassumed to be substantially constant in a machine of the type illustrated and, in any, event, not

to laryito such an extent as will 9W5? w st ated impact effects under any operating conditionsof the machine. a

After having reached the end of portion 44 of the slot with the elastic tension of the operated parts and the pressure on the follower nearly relieved, the condition in the mechanical system: approaches the point where there is very little pressure of the cam roll 34 against side 36 of the" slot and the follower soon thereafter may begin to move away from the side due to the inertia and friction of the moving system. After the follower moves with uniform velocity, the only factors acting to prevent the moving system from continuing to move at uniform velocity, are the de celerating effects of friction inherent in th'e-bear tends to cause the follower to hug the same side 36 of'the slot somewhat beyond the point where uniform velocity is reached These factors may The decelerat- 15 'ings and pivotal connections of the system, to; 'gether with the resistance of the work performed, Th'egeffect 'of friction and work resistance thus,

be grouped together under thehead of total friopared with the velocity reducing pressure or negative accelerating effectof the cam slot for any one particular set of operating conditions inthe machine, therefore, determines the point at which the cam follower becomes'diseng aged from the side 36 of the cam slot. Between the sides of the cam slot, the follower moves alonga path corresponding' to the path of abody being uniformly decelerated, the rate of deceleration being regulated by friction. Thefree movement or cross-.

over of the follower requires but a brief-period unless the ,shapeof the succeeding cam slot por--' tion 46 is formedexactly to coincide with the follower movement as determined by the particular if "friction values existing at thetime. In case the cam slot portion 46 should'be so formed, this shape would coincide with the follower movement for only one speed and for only one value of friction in the machine, any'other values of speed or friction acting to cause forcible impact of-the follower .with side 38 of the slot, which impact would increase proportionately with the departure from said speed and friction value.

In the form of the invention-shown, the rate of decrease in pressure on the follower or in negative acceleration produced bythecam s'lot is'abruptly reduced, as indicated at 45 (Fig; 2 between slotportions 44and 46 from the high rate of decrease along portion to a relatively low rate of decrease, the negative acceleration'still being somewhat less than the deceleration 'due to minimum total fric-v tion, so that'with' the smallest possible amount of total friction in the system',the follower will still bein engagementwith side 36 of the cam slot at the beginning of portion 46. Thereaftenas the pressureon the'follower is decreased ata lowrate,

' a'point will-be reached where thelnegativeaccelf eration equals the deceleration'of friction' and the 7 pressure on the follower is reduced to zero; The i follower will then'leave side 36'and engage side 38 of the slot. As the value' of total friction in the machine increases under different operatment with the first side 36 of the slot for alo'nger "ing conditions, the follower will remain in engagetime. By properly extending the length of the slot portion 46 in which the pressure or negative acceleration of the cam slot is reduced at a low rate, the velocity of the follower with respect to the slot, which velocity causes the impact at the end of the cross-over period,- maybe made substantially less than heretofore considered possible for any range of friction values. The rate of acceleration change between the portions 44 and 45 being made abrupt, as distinguished from being gradual or progressive, insures that the crossover will occur with certainty only along portion 46 of the slot. 7

The degree of impact produced by the follower striking the side 38' of the cam slot after the crossover may also be made substantially uniform throughout a definite range of friction values in the machine, by reducing. the pressure or negative acceleration of the slot movement at a uniform rate along slot'portion 46. By proportioning the curvatures of slot portion 46 at the be ginning to effect a pressure below and at the end to effect a pressure above the decelerating forces of friction in the system, the follower will, therefore, always shift from one side of the slot to the other with uniform impact for any values of friction existing under different normal operating conditions in the particular mechanism.

After the follower has definitely engaged the second side 38 of the cam slot, the rate of velocity decrease or the negative accelerating force of the cam may be gradually reduced along a follower slot portion 48 to a point where it equals the average decelerating effect of friction, after which the negative accelerating effect of the cam slot on the follower may be instantly reduced to zero at the end of the portion 48, in case the succeeding portion 42 of the cam slot is in the form of a dwell. Instead of dropping to zero, other accelerating forces may be imparted to the follower without actually bringing the follower more nearly to rest, since the decelerating effect of friction is substantially equal to any other force imparted to the follower along the portion 42 of the cam slot, and no oscillatory engagement between the slot sides will be produced. The rate at which the negative acceleration of the slot portion 48 may be reduced is limitedas in the cam' portion 44, only by the elasticity and mass of the parts.

Briefly, therefore, the present invention consists in first reducing the negative accelerating pressure of the cam slot ata high rate and then abruptly reducing the rate of negative acceleration change, to a relatively low rate at the beginning of the portion 46 of the cam slot after the pressure of the follower on one side of the cam slot is nearly relieved so that the follower will surely cross over from one side 36 of the cam slot to the other 38 along portion 45. The preliminary portion 44 of the slot in advance of portion 46 acts progressively to release substantially the tension in the operated parts, so that the mechanical system moved by the follower will not have set up within itself a series of sustained oscillations to interfere with the actual period of cross-over. By this arrangement, cross-over with a minimum impact may be assured. The only other limitation which may desirably be observed is in maintaining the maximum pressure angle or inclination of the cam slot below a reasonable limit, and preferably below the usual 30 degree angle. With such limitations the shapes of all the cam slots'of a sewing machine of the type referred' to, may be modified with marked improve ment in operation of the machine both to durability and as tc inereased speed of operation over that heretofore possible.

A more'detailed and specific description of the manner of applying these limitations to the cams in thednac'hine illustrated will now be given.

Referring more particularly to Figure 1, it is apparent that the cam slot is divided into a series of consecutive elementary movements in the direction in which the follower is capable of being actuated, each for the purpose of transferring the follower between positions. at different distances from the cam shaft l2. The elementary movements may terminate in dwell portions in which the cam slot is concentric with the shaft I 2, or they may terminate more abruptly in portions which cause movement in other directions. Obviously, no motion is imparted to the follower along the dwell portions, so that once movement of the follower has been stopped, no special consideration is required until 7 another movement is begun. The elementary movedwells. 'The' characteristic shape of each ele-* I mental movement, as will be described, is made substantially similar to that of another, all corresponding points of each being made proportion al to the extent of movement required and to the time of angular displacement in the cam between the limits of movement. The elementary movement included within the radial lines 62 to 64, is selected as an example of how each movement may be formed, according to the present invention.

The diagrammatic illustration of the characteristic shape to be applied to the movement 62 to 64 is shown in Fig. 2, and is divided into a series of unequal; portions by vertical lines 10. The spacings in a vertical direction correspond to the movement in'a radial direction on the cam, and the spacings in a horizontal direction represent the relative time or amount of angular rotation required for the movement, the space portions between the vertical lines being so chosen as to substantially separate the times in which different characteristics of the moving mechanical system connected with the follower are effective in reducing the impact along those portions. The portion 40 of the cam slot may be assumed to be a dwell, and the cam follower 34 is illust'rated with an exaggerated amount of clearance between the sides 36, 38 of the slot so as to more clearly illustrate the features of they invention.

While the follower 34 is operated upon by the dwell portion 46, it is impossible to determine the relative positions of the follower and the slot sides, so that in starting a given motion, aportion 12 cf the slot is formed with a very gradually increasing velocity, and the degree of acceleration, as indicated in the corresponding lower part of Fig. 2, starts from zero and is increased at a low uniform rate. At the end of the slot portion E2, the follower 3 3 is definitely in'engagem'ent with the slot side 3%, the total amount of movement within this portion being made greater than the clearance or lost motion of the operated parts, the maximum accelerationbeing such as to reduce to a minimum the impact of thelfollower against the slot side.

After the follower has definitely engaged the side 36 of the slot, the force of acceleration may be increased more rapidly along a portion 14 until .the greatest direct pressure which it is desired to apply tothe follower is reached. The

increase in accelerationlis illustrated as being, uniform, but may be made to vary at any'desired rate until the end of the portion 14. The length 'of time required for this movement, however,

. shouldbe sufficiently long to'prevent oscillation of the operated parts, as previouslydes'cribed in connection with portions and 48. I

At the end of slot portion" there is arranged a portion 16 of uniform acceleration and uniformly V increasing velocity terminating at e such time "as theinclinatio'nof the slotfappr'oximates the greatest pressure'anglewhich it is desiredtto employ.

The velocity of the cam during the next portion 44 reaches a maximum as, the accelerating force is being rapidly reduced. Until the zero acceleration point is reached, the cam follower remains against the same side 36 of the cam slot that it originally engaged during start of the motion. However,

the cam follower will continue in engagement 7 unrestrained path until engagement, with the other side 38 occurs. After the portion 44 is terminated, therate of change innegative ac-' celeratio'n is decreased abruptly so that it increases more slowly along the succeeding slot portion'46; When the point H in the :portion 46 is call cleaned and oiled reached,-where the negative acceleration f orce, of

the cam is greater than the minimum decelerating force of friction on the operated system, the followermay'begin'to cross from one side of the slot to the other.

formed. a V I a 7 To cause the. follower to surely cross over to the side 38 of the slotv negatively accelerated movement produced by-the c'am portion 46 is increased: at the slow rate, above referred to, until a value of negative acceleration force is reached at a point 18 which is greater than any decelerating effect produced by the maximum total friction including full operating load resistance of .the .mechanical system. 'With' small values of V friction, the follower will cross over from side 36 to side 38' just .beyond the point 14 and, with large'values of friction, thecross-ov'er will take place later. The follower will, therefore, always 7 shift from one sideof'the slot to the other along the slot'portion 46'.

The next portion of, the cam slot is arranged to reducethe 'negative ac'celeration force to zero, and since the motion shown in'Figure 2 terminates in a. dwell portion 42, the portion 48 is,

. characterized by a negative acceleration decreas- "ing more rapidly than-the rate .of increase in negative acceleration of theprevious slot portion in order to reach the point of zero acceleration quickly;v Since the cam follower already has 7 The minimum'decelerating forcelof friction is determined with the bearings while no work is'being .per-

crossed over and the velocity is being reduced,

the rapidity with which theinegative acceleration is increased thereafter causes no furthershift V of pressure from one side of the slot tothe other;

This rapidly decreasing negative accelerationterminates at a point where the negatively accelerated movement is approximately equal to or greater than the average deceleration produced by friction in the moving systema- When; this point is reached, the negative acceleration is instantly decreased to zero, and no oscillations or substantial impacts of the. follower occur between the slot sides because the amount of energy stored in the" moving system. is effectively 'ab-' "sorbed by the frictional force without impact."

If any other motion is to be imparted: tothe cam follower directly at the beginningori at .the end of the movement just described, .inplace 0f the dwellportions 4D or 42, respectively, an ad- J'acent slot portion of the proper shape may be connected directly to the'portion14 or.46 without reducing the negative acceleration entirely ,to

zero, and'since the follower is already in engagement with the respective side of theslot, the'ac= celeration may be applied .rather abruptly to move the follower in the opposite direction.

By preventing the follower from leaving one 7 side of the cam slot while the acceleration is being reduced to zero at the end of each motion unit, and then by reducing the negative acceleration to a predetermined minimum, the impact between the follower 'and the slot'may be diminished we. pointrwhere it is not troublesome for the maximum speed at which the, cam shaft is rotated. With the slot proportioned as described, w)

the impact of the follower will not"increase' with,

a'reduction in speed of the machine,so that the impact may be kept below apredetermined degree at all speeds. I

The amount of elasticity or silience in the moving system may, for all practical purposes, be assumed as constant, since this characteristic. does not change with different operating conditions One limiting value of negative acceleration foreach portion 14, 44 and 48 for any speed of cam rotation below the maximum. However, the friction may change from time to time and with different kinds of the 'work being operated upon. a

1 In considering the effecton impact of chang ing values of total friction in the machine, it will be assumed that the intensityvof impact is dependent upon the maximum velocity of the follower relatively to the sides of the cam slot as it crosses from'one side to'the other of the slot.

. The velocity is also governed by the amount of lost motion in the mechanical system which ,per-

mits an abrupt change invelocity. between the parts. 7 This lost motion may be considered uniform throughout the follower movement, since it is composed of a number of factors which tend to result in a rather, definite average. a A

measure of rea In order to illustrate the motion of the ronower during the time .it crosses from one side '36' ofthe cam slot to the other side 38, the velocity and acceleration curves of Fig. 2 may be referred, to. All vertical distances between the cam slot and the zero ordinate 19 represent areasunder J the curve of velocity, and alleverticaldistances 7 between the velocitycurve and its zero ordinate B8 are equal to areas between'the acceleration curve and its zero ordinate 82. This is as a result of constructing these curves in the proportions required by the equations of actual physical 3.15" of the cam slot, therefore, will besufficiently low sc /mess movements of the slot sides in the line of follower movement; I

The vertical distancep represents the amount of equivalent lost motion in the mechanical system, indicated'for purposes of illustration'as being wholly between the follower 34 and the cam slot portion 46 at the point where the follower contacts with the side 38 after having crossed from the side 36 of the slot. It is apparent that this lost motion is substantially uniform throughout portion 46; The cross-over occurs in a period of time t during which the follower moves along a free path m in the form of a parabola, and departs from the curve of the cam" slot by the amount p.- The distance p is, therefore, equal to the distance after a time 15 between points along the path of a freely moving body affected only by friction which describes a parabola and. along the side of the cam slot in the form of a cubic curve, respectively, from the point of tangency of these curves. The impact is produced by the difference of velocities of the follower and slot side at the end of period t after having travelled the distance p.

The difference between the velocity curve 1' of the follower and the velocity curve of the cam slot at the end of the time period t is indicated at v and is a measure of the intensity of the impact with which the follower engages the side 38 of the cam slot. The difference of acceleration which causes the difference of velocity v is represented in the acceleration diagram by a, which is the difference in acceleration force, at the end of period t, between the constant decelerating effect f of friction on the follower and the negative acceleration of the cam slot which is made to increase at a uniform rate.

The expression of the distance p vertically between the parabola m and the cubic cam curve after the time period t from their point of tangency takes the form Where it is the rate of acceleration change of the cam slot and, correspondingly, the expression of the distance 1) vertically between the straight line 12 and the parabolic velocity curve of the cam slot takes the form,

Substituting '0 into the expression of p,

But, since u and t, according to the next to last equation, vary together in the same direction, p being a constant because it is known that the lost motion is uniform, there is but one value each for v and t which satisfies the last equation. Therefore, 12 remains the same at any point along the slot portion 46 and the velocity and impact of crossover for a slot having a cubic curve remain uniform with changing values of friction. The only effect of changing frictional values is to cause the follower to cross from one side to the other of the slot earlier or later along the portion 46, the length of time required by the crossover period remaining the same.

In the sewing machine cam illustrated, the relative length of time allotted to the cross-over slot portion 46 is the largest in each elementary motion unit. The tension releasing slot portions 52, 44 and 48 are of sufficient length to produce the desired effect as quickly as practical, and the lengths of the remaining slot portions 50 and '53 are more or less arbitrary and maybe increased. or decreased to a reasonable extent in providing for more efiicient operation'of the other portions; It has been found that the relativeproportions, as illustrated in Figure 2, between the'v'ertical lines, are'elfective to provide unusually quiet operation at higher speeds of the machine than herea tofore considered possible."

In applyingthe motion unitof Figure 2 to the various elementary motions required in the machine, the-individual"portions" of eachunit are laid om proportionally as angular displacements along-the elementary-m tion of the-cam, as shown -Figure l-gai-id the displacement radially of the cam is adjusted to equal the displacement required by the elementary cam motion, the intermediate points of displacement being proportioned accordingly. In some instances it may not be necessary to apply the motion unit of the invention to all of the elementary motions in the machine, but only to those in which the greatest displacement of the follower takes place, and in those where undesirable impact is definitely located.

The description given above is based upon the presumption that the amount of lost motion in the mechanical system is substantially constant, but in certain cases the amount of lost motion may increase with the movement of the follower. This increase of lost motion, however, may be compensated for along the slot portion 46 by causing the negative acceleration of the cam slot to increase at a non-uniform rate, and in case this change in lost motion may be caused by angular deviation of the slot, the rate of increasing negative acceleration would, as a result, be increased slightly to compensate for the change of lost motion from the inclined part of the slot portion 46 to the dwell portion where the lost motion would be smallest.

The nature and scope of the present invention having been indicated, and a machine embodying the features of the present invention in their preferred form having been specifically described, what is claimed is:

1. A machine of the type described having, in combination, an operated part, a cam follower and connecting links comprising a mechanical system of inherent mass, elasticity and friction, and a cam in the machine having a continuous closed slot in which there are a number of elementary unidirectional movements imparted to the follower loosely engaging the slot as the cam is rotated, at least one of the movements being effected at its beginning by cam slot portions for increasing the velocity of the follower by pressure of one side of the slot, at its end by slot portions for decreasing the velocity of the follower by pressure of the other side of the slot, and between its beginning and end by two successive slot portions in the first of which the initial pressure on the follower decreases progressively at a relatively rapid rate, limited only sufii'ciently to prevent complete interruption of pressure, in the second of which the pressure decreases at a relatively low rate for a sufficient length of time to cause the pressure on the follower against the first mentioned side of the cam slot to be entirely relieved and transferred to said other side of the slot and between which two portions there is an abrupt change in rate of pressure decrease to insure transfer of follower pressure only along the slot portion of low decreasing pressure rate.

2. A machine of the type described having, in

combination, an operatedpait, a camfollower andconnecting links comprising a mechanical system of inherent mass, elasticity and friction, and a cam in the machine having a continuous closed slot in which there are a number of elementary unidirectional movements imparted to the follower loosely engaging the slot as the cam is rotated, at least one of the movements being efiected. at its beginning by cam slot portions for increasing the velocity of the follower by pressure of one'side of the slot, at its end by slot portions for decreasing the velocity of the follower by pressure of the other side of the slot, and between its beginning and end by two successive slot portions in the first of which the initial pressure second of which the pressure decreases at a relatively low uniform :rate for a suflicient length of time to cause the pressure on the followers against the first mentioned side of the cam slot to be entirely relieved and transferred with uniform impact for all values of friction in the mechanical system to said other side of the slot, and'between which two portions there is an abrupt change in rate of pressure decrease to insure transfer of the follower pressure only along the slot portion of low decreasing pressure rate.

LAURENCE E. TOPHAM. 

